An Etymological Dictionary of the German Language/baß
baß (2.), compar. adv., ‘better,’ from the equiv. MidHG. baȥ, OHG. baȥ; comp. OSax. bat-bet, AS. bet from batiz (Goth. *batis); it is an old adv. from the adj. discussed under besser. The almost invariable use at present of the adv. besser, instead of the older baß, is due to the fact that the formation of the adv. was no longer understood, and that the adj. at the same time has in every case assumed an adv. function.